Most electronic systems include input/output (I/O) pins that can exchange data with external devices. Some of these electronic systems can include fixed-functionality I/O pins, such as a dedicated reset pin or I/O pins that are preset to a particular drive state, while other electronic systems can have I/O pins that are programmable to one of several states, such as an input drive state, an output drive state, or a high impedance state.
Programmable I/O pins are often configured into one of the available states by a microcontroller of the electronic system, possibly in conjunction with firmware. For example, upon system initiation or after a reset, the microcontroller and corresponding firmware can configure the programmable I/O pins to a particular drive state as soon as power has sufficiently ramped up and the electronic system has become fully operational. Prior to the electronic system becoming fully operational, i.e., before the programmable I/O pins can be configured by the microcontroller, many electronic systems will hardwire their programmable I/O pins to a default state, such as the high impedance state.